Many organizations, such as corporations or government entities, have requirements, whether legal, financial, medical, educational, or private regulations, that require event logging. Logs of events, such as computing events or real world events, are often logged in log files or databases by computing systems. Such a record of events can be modified by malicious parties prior to review by an administrator or auditor.
Verifiable logs, using one-way hashing algorithms, have been used to validate log entries. These logs use a hash chain where each log entry's hash is dependent upon all log entries and their hashes that occurred previous to the log entry. In addition to hash chains, tree logging structures have also been suggested as a more efficient data structure to build tamper-evident logs.